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ZCI Insert

03-14-2010, 11:09 AM

I know there have been a lot of posts on here concerning zero clearance inserts but I was wondering, when you make a new one what do you do about the riving knife? do you just not use it because I really would like to continue using it. This is on a 4511 and also do you use the screw to attatch it to the table or rely on a good tight fit?

Comment

You can cut a slot for the riving knife. I didn't use the screws or levelers on mine, just friction fit and a dab of silicone on each corner and then level the insert with the table.

The problem you run into with the original riving knife setup and home made inserts is that the teeth on the anti-kickback pawl will dig into most typical ZCI insert material (wood, plastic etc) when you attempt to lower the blade. If you make you own I'd suggest using formica or a phoenelic type material for the surface. Good luck, Mike

Comment

I know there have been a lot of posts on here concerning zero clearance inserts but I was wondering, when you make a new one what do you do about the riving knife? do you just not use it because I really would like to continue using it. This is on a 4511 and also do you use the screw to attatch it to the table or rely on a good tight fit?

The R-4511 is one of the easiest inserts there is to make. Here's how I do it.

First, select your stock. I used some left over floor laminate. To set the width, I remove the stock insert, flip it over and use it to set the distance of the fence to the blade. I reinstall the stock insert, and rip my stock to the proper width. After this, I move over to the miter saw, and again use the stock insert to set the length.

After cutting the rectangle, it's a simple matter of going over to the sander and rounding the corners. The laminate is only 3/8" thick, so I install 4 short screws from underneath for leveling purposes. I might mention, to go ahead and drill a finger hole, makes it easier to get in and out.

Once it's leveled up to the saw top, I install a smaller diameter blade than 10" so I can get clearance to cut the slot. If it's a full kerf insert I'm making, I'll use one of the blades from my dado set. If it's to be a thin kerf, I'll use a circular saw blade.

Before you raise the blade through the insert the first time, you need to come up with a way to hold it down so it doesn't lift as your cutting. You can clamp a board, front to back on top, but what I did was slide the fence over the right side of the insert. I slid a shim under the fence, so it would hold down tight, and used a clamp to make sure the back of the fence didn't raise up.

Be careful here that you don't let the blade raise up into your metal fence.

Raise the blade slowly, all the way up, cutting the slot. Now you can remove the smaller blade, and install your 10". Again, secure the insert with your fence, and raise the 10" all the way up. This takes care of the blade.

Now to elongate the slot for the riving knife. I take the insert out, and set the stock insert back in for the time being. With the saw off.....and the blade raised to just over the thickness of the new insert, I set it down over the blade, upside down. I slide the fence over untill it touches, and lock it down. Now...using a shop built push block, NOT A PUSH STICK, I hold the insert down so I can control it.

I flip the switch on, and push the upside down insert forwards, extending the slot until I think it's long enough for the riving knife to clear. I don't cut all the way through, cause I don't screw my inserts down like the stock on, and I don't want to weaken that back edge.

When you think the slot's long enough, stop pushing, continue the down pressure on your push block, and flip the switch off. Don't move until the blade comes to a complete stop.

Put your new insert in, and see if your knife will clear. If you didn't cut the slot far enough back, you might have to do it a little more. Also...if your knife is a tight fit in your new insert, you might have to file/sand the slot a little so it don't try to hang when you raise it.

As for screwing down the new insert, I don't. It's a lot of trouble to screw and unscrew as many times as I change blades. On my first one, I placed a fender washer underneath, hanging off the back side, to catch under the table top at the back, so the insert couldn't lift from the rear. On my subsequent inserts, I haven't done this. I haven't had one lift yet, and if it did, I believe the knife would keep it from being thrown at me.

Anyway....this is how I do it. If you're not comfortable doing it this way, then by all means, find a comfortable way to extend the insert slot for you. Maybe a scroll saw?

Comment

The problem you run into with the original riving knife setup and home made inserts is that the teeth on the anti-kickback pawl will dig into most typical ZCI insert material (wood, plastic etc) when you attempt to lower the blade.

Good point Mike, and you're exactly right. At first, I chose to take the anti-kickback pawls off my guard to stop this problem. Then I built the shorty knife, and hung the guard on the wall.

I'M NOT SAYING DO THIS!

It's just that I've never had a saw with a guard/pawl set up, and I tried it for a couple of weeks, and decided I was more comfortable without it. I felt I had better control of the board without it.

I know this is a personal choice, and I'm not stupid enough to brag about never having an accident, or kickback. It can happen so fast.